Molding press

ABSTRACT

A LOW-COST, HIGH-SPEED PRESS FOR MOLDING PLASTIC ARTICLES HAVING A MOVABLE UPPER PLATEN AND A FIXED LOWER PLATEN WITH OPPOSED MATCHING DIES ATTACHED THERETO. THE UPPER PLATEN IS MOVED BETWEEN A REMOTE UPPER POSTITION TO A LOWER MOLDING POSITION AT HIGH SPEED BY A MOTOR-DRIVEN SUSPENSION SYSTEM. WHEN THE UPPER PLATEN IS IN THE LOWER MOLDING POSITION, A PLURALITY OF PLATEN STOPS ARE MOVED INTO LOCKING PLATEN AND MOLDING FORCE IS APPLIED BY MEANS THE UPPER PLATEN AND MOLDING FORCE IS APPLIED BY MEANS OF A FLUID-FILLED PRESSURE BAG POSITIONED BETWEEN THE DIE PLATES AND ONE OF THE PLATENS. THE PLATENS STOPS ARE ADJUSTABLE IN HEIGHT TO COMPENSTATE FOR VARIABLE HEIGHTS IN THE DIES USED WITH THE PRESS AND VERTICAL PLATEN GUIDES ASSURE MOLD ALIGNMENT THROUGHOUT THE RANGE OF MOVEMENT BY THE UPPER PLATEN.

R. J, GELIN MOLDING PRESS June 6, 1972 2 Sheets-Sheet 1 Filed Aug. 13,1969 W W H l. J @1 R. J. GELIN MOLDING PRESS June 6, 1972 2 Sheets-Sheet2 Filed Aug. 13, 1969 INVENTOR. A9055?? l 6.a /A/ W a, w w :im y,.Hlqw.. l ,M f0.5 0 /1 f 1,4/1: 2 /4 2 /U/J 7/ l /M @mm/@ a @i LL: 11Ma l. Il a@ I .HII l wh. QV yy 7J 7 ff i United States Patent Oce3,667,891 Patented June 6, 1972 U.S. Cl. 425-408 5 Claims ABSTRACT 0FTHE DISCLOSURE A low-cost, high-speed press for molding plastic articleshaving a movable upper platen and a fixed lower platen with opposedmatching dies attached thereto. The upper platen is moved between aremote upper position to a lower molding position at high speed by amotor-driven suspension system. When the upper platen is in the lowermolding position, a plurality of platen stops are moved into lockingposition to prevent upward movement 0f the upper platen and moldingforce is applied by means of a fluid-filled pressure ybag positionedbetween the die plates and one of the platens. The platen stops areadjustable in height to compensate for variable heights in the dies usedwith the press and vertical platen guides assure mold alignmentthroughout the range of movement by the upper platen.

BACKGROUND OF THE INVENTION This invention relates to a low-cost,high-speed press for molding reinforced plastic materials, such as glassfiber-reinforced synthetic resin articles, in which the ultimate moldingforce is applied by means of a fluid-inflatable molding bag. Morespecifically, the invention relates to a molding press in which movementof the upper press platen from an upper remote position to a lowermolding position is controlled by a high-speed mechanism operatedindependentliy of the fluid-inflated pressure bag, and in whichremovable mold or die plates may be attached to the opposed faces of theplatens for molding different objects. The press is capable of handlingmolds having various depths or draws and can apply a wide range ofmolding forces by selecting a suitable fluid pressure to be supplied tothe pressure Ibag which exerts the molding force.

Molding presses in which the molding pressure is applied upon the moldedarticle by means of a fluid-inflated bag which is inflated between apair of locked platens eliminate the need for expensive hydrauliccontrols. In such presses, such as those disclosed in U.S. Pats.2,411,043, 3,135,998 and 3,152,364, the upper and lower platens arelocked together and the entire vertical movement of the molds or dies iscaused by the inflatable bag. These prior art presses have thedisadvantage in that, if molds of various depths or draws are required,the length of the vertical movement may be excessive so that the timerequired to close the platen and apply molding pressure to the moldedarticle is long and also the amount of ination to effect such verticalmovement may extend the inflatable bag beyond its desired shape. Becausethe molding force applied is a function of the area of the bag incontact with the opposed platen surfaces, over-inflation of the bag willnecessarily reduce this area to require a higher pressure for a givenforce and also will stress areas of the bag not in contact with theplaten faces.

U.S. Pat. 2,869,174 also discloses a fluid bag-operated press in whichthe bag, upper platen and upper mold or die are lowered into position bya mechanical means and, after latching the upper platen to the lowerplaten, bag pressure is supplied to apply the molding force. While apress of this type is useful in reducing the time necessary to lower theupper platen into molding position, it requires manual alignment of theupper and lower platens prior to latching, and will not accommodatemolds of varying depths. In addition, due to the manner of positioningthe bag within a pocket between the upper die and upper platen, thistype of press does not present a large horizontal bag surface againstthe opposed die surface so that relatively high fluid pressures arerequired for a given molding force.

SUMMARY OF THE INVENTION It is a primary object of this invention toprovide a low-cost molding press which has none of the disadvantagesenumerated above with respect to presses of the prior art. This isaccomplished by means of a press having an upper and lower platformsupported by a xed frame in which a lower platen and its attached lowerdie rests upon the lower platform, and an upper platen is guided from anupper remote position to a lower molding position by means of guide barsfixed with relation to the lower platen so that the upper platen will beconstantly guided in vertical alignment with the lower platen. The pressalso includes a provision for locking the upper platform in its lower,molding position so that when the fluid bag is inflated, further upwardmovement of the upper platen will be prevented so that the bag force istransmitted to the article being molded. The press also includes meansfor varying the vertical position of the platen locks so that dies ormolds of varying depth or draw can Ibe interchanged.

Other objects and advantages of the present invention will be apparentto those skilled in the art from a following detailed description of thepreferred embodiment thereof, with reference being made to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a view in elevation of themolding press of this invention showing the upper movable platen and itsattached upper die in both its open, remote position and its closed,molding position;

FIG. 2 is a plan view of the molding press shown in FIG. 1;

FIG. 3 is a cross-sectional view in plan, taken along line 3-3 of FIG. 1and showing the details of the lluidinflatable bag used to apply themolding pressure;

FIG. 4 is a view in elevation of the molding press, similar to FIG. 1but showing the lluid pressure bag inllated to force the upper dieagainst the lower die to mold an article therebetween; and

FIG. 5 is a view in perspective of one of the platen locking deviceswhich, when actuated, prevents upward movement of the upper platen fromits lower molding position.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS, 1 and 2, apreferred embodiment of the molding press of this invention has a frameincluding four vertical supports 10 to which are secured a fixed, upperplatform 11 and a lower platform 12. Resting upon the lower platform`=12 is a lower platen 13 upon Whose upper surface is secured the lowermold or die 14. Pour vertically-extending guide pins 15 are secured tothe lower platen 13 at the corners thereof and extend upwardly towardsthe upper platform 11. As best seen in FIG. 4, the tops of the guidepins 15 may terminate in a point or ogive 16 which assists inrepositioning an upper platen, generally designated by reference numeral17, if it is raised above the tops of the guide pins 15.

The upper platen 17 includes an upper bolster plate 18 and an upperplaten plate 19 to which is attached the upper mold or die half 20 inalignment with the lower die half 14. As previously stated, the press ofthis invention is designed to accommodate a plurality of various typesof die halves so that the upper and lower die halves -14 and 20 areremovably secured in a conventional manner to their respective platens13 and 19. In addition, it should be noted that the horizontal area ofthe platens 13 and 17 is sufficient to accommodate large sized dies sothat standard dies may be interchanged without necessity of any specialdesign which might be necessary to accommodate the vertically-extendingguide pins which are positioned at the corners of the lower platen 13.

Extending through the bolster plate 18 and upper platen plate 19 arefour openings 21 positioned to receive the vertically-extending guidepins 15 so that, as the upper platen 17 is lowered towards the lowerplaten 13, vertical alignment of the platens 13 and 17, and thus theirassociated dies 14 and 20, is maintained. It will be understood bypersons skilled in the art that appropriate indicia upon the platenfaces can be used to position the diev halves 14 and 20 to assure propermating when the platens 13 and 17 approach one another. The openings 21are defined by sleeves 22 which are secured to the upper platen plate 19and extend through cylindrical passages in the bolster plate 18 so thatthe sleeves 22 can move vertically relative to the bolster plate 18.

Positioned between the opposed surfaces of the bolster plate 18 so thatthe sleeves 22 can move vertically relabag, generally designated byreference numeral 23 and best seen in FIG. 3, which consists of aplurality of parallel flat tubes 24 of a reinforced flexible material.The tubes 24, as shown in FIG. 3, are completely closed at their upperends and have their lower ends connected to a common air manifold 25 sothat air pressure supplied` to the manifold 25 through an air supplyline 26 will inliate the tubes under equal pressure. As seen in FIG. 1,with the tubes 24 of the air bag 23 in unintlated position, they lieflat between the bolster plate 18 and upper platen plate 19 so thattheir horizontal surface area adjacent these two plates is substantiallyequal to the horizontal area of the plates 18 or 19. Because the forceapplied to the molded material is a product of the air bag pressuretimes the area in contact, a larger contact area requires less airpressure for a given force, as will be subsequently explained.

The mechanism for raising and lowering the` upper platen from an upperremote position, as shown in phantom in FIG. l, to a lower moldingposition, as shown in solid line in FIG. 1, consists of a cablesuspension system including an electric motor 27 secured upon the upperplatform 11 with an appropriate gear reduction box 28 having a pair ofcable drums 29 and 30, as seen in FIG. 2. Suspension cables 31 and 32are wound upon the drums 29 and 30, respectively, and extend overpulleys 33 and 34, respectively, positioned at the corners of the upperplatform and downwardly within the press frame. The ends of cables 31and 32 are secured to a dog 35 which extends outwardly from each of thesleeves 22 secured to the upper platen 19. When the electric motor 27turns the drums 29 and 30 on the gear box 28, in either direction,cables 31 and 32 will be wound or unwound to raise or lower the entireupper platen 17 as it is guided by the guide pins 15 from its upperremote position, as shown in phantom in FIG. 1, to its lower moldingposition, as shown in full line in FIG. l.

Secured to an inner face of each of the vertical supports 10 is a platenlock mechanism, generally designated by reference numeral 36, which, asbest seen in FIG. 1, includes an air cylinder 37 containing a piston 38which is connected through a piston rod 39 to a wedge-shaped stop member40. The stop member 40 is guided in its horizontal movement by a slide41 and is adopted to move within the slide 41 from a remote or openposition clear of the path of vertical movement of the upper platen 17to a closed position. In its closed position, the stop member 40 extendsover a wedge-shaped seat 42 secured to the upper surface of the bolsterplate 18, as shown in FIG. 1.

A pair of air lines 43 and 44 from an air header 45 supply air to eachend of the air cylinder 37 so that pressure selectively applied toeither of the air lines 43 or 44 will move the piston 38 and thus thestop member 4G between its open and closed position. The air supplylines 43 or 44 of their respective platen locks 36 are connected to acommon air header 45 or 46, which headers are in turn connected throughan air control valve 47 which is manually operated to supply airselectively to either header 45 or 46 so that each of the platen locks36 are moved simultaneously together with the others from their open toremote positions.

The press of the preferred embodiment described includes a number ofelectrical or pneumatic controls for limiting the vertical movement ofthe upper platen 17 and controlling the movement of the platen locks 36.These controls are 'schematically shown and are briefly described asfollows.

A rst limit switch 48 is secured to the frame above the upper remoteposition of the upper platen 17 and is interconnected in the powersupply to the electric motor 27 so that, when the upper platen 17reaches its uppermost position, Ias shown in phantom in FIG. l, the rstlimit switch 48 is opened to disable the motor 27 and to prevent furtherupward movement.

A second limit switch 49 is secured to the frame with its movable arm incontact with the cable 32 supporting a portion of the upper platen 17,as shown in FIG. l. The limit switch is interconnected with the powersupply to the electric motor 27 so that when the upper platen 17 ismoving downwardly to a molding position adjacent the lower platen 13,continued movement of the cable 32 Will slacken he cable 27 to open thesecond limit switch 49 to stop f ther rotation of the motor 27. Thelimit switch 49 could be placed adjacent the lower platen 13 but, if sopositioned, would require adjustment in order to compensate for variablemold depths, as previously explained.

A third limit switch 50 is positioned on the frame adjacent one of theplaten locks '36, as shown in FIG. l, so that it is actuated by movementof the stop member 40 to its closed position. This third limit switch 50is interconnected with the power supply of the motor 27 to disable themotor 27 when the stop member 40 is in its locked position so that thecable system cannot attempt to raise the upper platen 17 against thestop members 40.

Operation of the press thus described is as follows. Starting with theupper platen 17 in its upper remote position, as shown in. phantom inFIG. 1, the sheet molding material or other molding compound is placedupon the lower die 14 on the lower platen 13 and the motor 27 isenergized, by means of the control switch 51 shown in FIG. 1, to lowerthe upper platen 17 to its molding position, as shown in full line inFIG. 1. When the upper platen 17 reaches its molding position, as willbe determined by its resting upon the material to be molded or byadjustable mold stops (not shown), the continued rotation of the motor27 will cause the cable 32 to slacken, thus actuating the second limitswitch 49 to shut oi further movement of the cable system. At this time,the operator will manipulate the air control valve 47 to apply airpressure through the air lines 44 which will cause the stop members 40to move to their closed position, as shown in FIGS. 1 and 4. Theoperator will next move an air control valve 52 to admit air underpressure to the supply line 26 to the air bag 23 which will inflate eachof the air tubes 24 positioned between the bolster plate 18 and upperplaten plate 19. `Inflation of the tubes 24, as shown in FIG. 4, willforce the upper platen 19 and its associated die half 2t) downwardlyupon the molding material to apply the proper molding force thereto. Aspreviously stated, the proper molding force is a function of thepressure supplied to the air tubes 24 and the Iarea of surface contactwith the tubes. A simple pressure adjustment valve can be included inthe air supply system to the air bag so that the desired amount ofmolding force can be obtained for any type of molding material andconguration of the die.

After the molding force has been applied and held for a suliicient time,the operator then switches the air control valve 52 to its otherposition to release the pressure from the air tubes 24, and the stopmembers 40 are retracted to their remote positions by movement of theair valve 47 to supply air to the pistons 38 through the supply lines43. The upper platen 17 is then raised by the motor 27 and itsassociated controls towards its upper remote position. When the upperplaten 17 reaches its upper position, it contacts the first limit switch48 to stop the motor control from further movement. In this upperposition, the molded part is unloaded and the new supply of moldingmaterial is placed upon the lower die and the process is repeated.

As previously explained, one of the advantages of the present inventionis that it can be used to accommodate a series of different molds ordies in which the depth of the draw or height of the article to beformed is varied, This is accomplished through the use of adjustableplaten locks 36 which can be positioned at differing elevations alongthe frame of the press. The means for adjustably positioning the platenlocks 36 is illustrated in FIG. 5, which shows a portion of one of thevertical supports with a plurality of stepped teeth 53 extendingvertically along its length. The slide 41 holding the stop member 40 andair cylinder I'37 is secured to a plate 54 whose inner surface hascorrespondingly-shaped teeth which interlock with the teeth 53 on thevertical support 10. One or more threaded screw members 55 are providedto secure the plate 54 at the desired elevation on the vertical support10. The operator, when changing from one set of molds to another, needonly reposition the four platen locks 36 at the desired height on thevertical supports 10 and then the molding operation can automaticallyproceed as previously described.

The preferred embodiment of the invention thus described has theadvantages of a uid bag molding press of the type previously used in theprior art in that it eliminates the relatively high cost of hydrauliccontrols necessary to supply high molding forces. The press of theinstant invention has the further advantage in that it is adapted toaccommodate molds of various designs and depths, will move the upperplaten at high speed from its upper remote position to its lower moldingposition, and will maintain the platen in vertical alignment with thelower platen at all times during this high-speed movement. The press ofthe instant invention also includes the aforementioned safety featureswhich prevent the unintentional actuation of the high-speed upper platencontrol when the platen locks are actuated, and further includes asimple pressure regulator control for selectively varying the moldingforce upon the objects to be molded. Other advantages of the inventionwill be apparent to those skilled in the art, and and variousmodifications thereof may be made without departing from the scope ofthe following claims.

`I claim:

1. A molding press for plastic articles comprising, in combination, afixed lower platform surrounded by a plurality of vertical supportswhich extend upwardly and terminate in a fixed upper platform, a fixedlower platen adjacent said fixed lower platform with a lower moldresting upon said lower platen, a movable upper platen positioned withinsaid vertical supports and supporting on its lower surface an upper moldin vertical alignment with said lower mold, said upper platen and moldbeing slidably associated with said vertical supports and movable in avertical direction from an upper open position adjacent said upperplatform to a lower closed position, a plurality of suspension cablessecured to said upper platen and extending upwardly to said upperplatform, motor means for paying out or winding up said suspensioncables whereby movement of said upper platen and mold between theirupper open and lower closed position is controlled solely by said motormeans, a plurality of platen locks adjustably secured to said verticalsupports, each of said platen locks having an engaged position whichprevents passage of said upper platen and a retracted position laterallyremote from the vertical path of said upper platen with means securingsaid platen locks to said vertical supports being selectively adjustablesuch that the vertical position at which they interfere with movement ofsaid upper platen can be selected, whereby said platen can be moved athigh speed from its said open to its said closed position and wherebysaid platen locks can be selectively engaged to interfere with movementof said upper platen at a selected height above said lower platen.

2. The molding press of claim 1 wherein said means securing said platenlocks to said vertical supports cornprises a plurality of stepped teethextending vertically along said vertical supports and at least onecomplementarily shaped tooth on the adjacent surface of said platenlocks whereby said tooth and teeth can be interlocked together at aselected position along said vertical support.

3. The molding press of claim 1 which further includes a controlmechanism carried by one of said platen locks and operably connected tosaid motor and elective to disable said motor only when said platenlocks are in engaged position.

4. The molding press of claim 3 wherein said control mechanism carriedby said platen lock is a limit switch for sensing the condition of saidplaten locks and effective to disable said motor only when said platenlocks are in engaged position.

5. The molding press of claim 1 which further includes a fluid pressureexpansion member positioned between one of said platens and itsassociated mold, said expansion member having a deflated state and astate of vertical expansion whereby, when said molds are in closedposition with said platen locks in engaged position to prevent furtherretraction of said movable upper platen, fluid pressure applied to saidexpansion member urging it towards its said expanded state will forcesaid molds together.

References Cited UNITED STATES PATENTS 2,363,779 11/1944 Duffy et al18-17 E UX 2,717,421 9/ 1955 Beeson 18-17 C 2,869,173 1/ 1959 VanHartesveldt et al.

18-16 H 3,089,188 5/1963 Hoffman 18-16 C 3,135,998 6/1964 IFowler, Jr.,et al. 18-19 P 3,191,235 `6/1965 Rougement 18-16 C X 3,195,186 7/1965Gauban et al. 18-30 LA X 3,242,533 3/1966 Wintriss 18-16 C 3,262,158 7/1966 Von Reimer et al. 18-30 LA 3,309,739 3/ 1967 Trueblood 18-30 LA2,739,749 3/ 1956 Davidson 10D-269 A UX 3,262,164 7/ 1966 Meves 164-3413,465,386 9/ 1969 Brown 18--30 L A 3,353,221 11/ 1967 Barnett et al.18-43 ROBERT L. SPICER, JR., Primary Examiner U.S. Cl. X.R.

10G- 219, 269; 425--Dig. 19, 411, 390, 450

